KAUNAS UNIVERSITY OF TECHNOLOGY Dr. Viktoras GRIGALI¥¾NAS (Kaunas University of Technology, Technological

  • View

  • Download

Embed Size (px)

Text of KAUNAS UNIVERSITY OF TECHNOLOGY Dr. Viktoras GRIGALI¥¾NAS (Kaunas University of...






    Summary of Doctoral Dissertation

    Technological Sciences, Materials Engineering (08T)

    2017, Kaunas

  • This doctoral dissertation was prepared at Kaunas University of Technology,

    Faculty of Chemical Technologies, Department of Polymer Chemistry and

    Technology during the period of 2013–2017. The studies were supported by the

    Lithuanian Council of Science.

    Scientific Supervisor:

    Prof. Dr. Saulius GRIGALEVIČIUS (Kaunas University of Technology,

    Technological Sciences, Materials Engineering – 08T).

    Editors: Dovilė Dumbrauskaitė (Publishing house “Technologija”)

    Inga Nanartonytė (Publishing house “Technologija”)

    Dissertation Defence Board of Materials Engineering Science Field:

    Dr. Viktoras GRIGALIŪNAS (Kaunas University of Technology,

    Technological Sciences, Materials Engineering, 08T) – chairman;

    Assoc. Prof. Dr. Mindaugas ANDRULEVIČIUS (Kaunas University of

    Technology, Technological Sciences, Materials Engineering, 08T);

    Prof. Dr. Habil. Albertas MALINAUSKAS (Center for Physical Sciences and

    Technology, Physical Sciences, Chemistry, 03P);

    Dr. Jūratė SIMOKAITIENĖ (Kaunas University of Technology, Physical

    Sciences, Chemistry, 03P);

    Dr. Aivars VEMBRIS (University of Latvia, Technological Sciences, Materials

    Engineering, 08T).

    The official defence of the dissertation will be held at 2 p.m. on the 2nd of

    October, 2017 at the public meeting of Dissertation Defence Board of Materials

    Engineering Science Field in the Dissertation Defence Hall at Kaunas University

    of Technology.

    Address: K. Donelaičio str. 73, 44029, Kaunas, Lithuania.

    Tel. no. (+370) 37 300042; fax: +370 37 324144; e-mail doktorantura@ktu.lt

    The Summary of the Dissertation was sent on the 1st of September, 2017.

    The doctoral dissertation is available on the internet (http://ktu.edu) and at the

    library of Kaunas University of Technology (K. Donelaičio str. 20, 44239

    Kaunas, Lithuania).

    mailto:doktorantura@ktu.lt http://ktu.edu/






    Daktaro disertacijos santrauka

    Technologijos mokslai, medžiagų inžinerija (08T)

    2017, Kaunas

  • Disertacija rengta 2013–2017 metais Kauno technologijos universiteto

    Cheminės technologijos fakulteto Polimerų chemijos ir technologijos katedroje.

    Mokslinius tyrimus rėmė Lietuvos mokslo taryba.

    Mokslinis vadovas:

    Prof. dr. Saulius Grigalevičius (Kauno technologijos universitetas, technologijos

    mokslai, medžiagų inžinerija, 08T).

    Anglų kalbos redaktorė:

    Dovilė Dumbrauskaitė (leidykla „Technologija“)

    Lietuvių kalbos redaktorė:

    Inga Nanartonytė (leidykla „Technologija“)

    Medžiagų inžinerijos mokslo krypties disertacijos gynimo taryba:

    Dr. Viktoras GRIGALIŪNAS (Kauno technologijos universitetas, technologijos

    mokslai, medžiagų inžinerija, 08T) – pirmininkas;

    Doc. dr. Mindaugas ANDRULEVIČIUS (Kauno technologijos universitetas,

    technologijos mokslai, medžiagų inžinerija, 08T);

    Prof. habil. dr. Albertas MALINAUSKAS (Fizinių ir technologijos mokslų

    centras, fiziniai mokslai, chemija, 03P);

    Dr. Jūratė SIMOKAITIENĖ (Kauno technologijos universitetas, fiziniai

    mokslai, chemija, 03P);

    Dr. Aivars VEMBRIS (Latvijos universitetas, technologijos mokslai, medžiagų

    inžinerija, 08T).

    Disertacija bus ginama viešame medžiagų inžinerijos mokslo krypties

    disertacijos gynimo tarybos posėdyje 2017 m. spalio 2 d. 14 val. Kauno

    technologijos universiteto disertacijų gynimo salėje.

    Adresas: K. Donelaičio g. 73-403, 44249 Kaunas, Lietuva.

    Tel. + 370 37 300 042; faks. + 370 37 324 144; el. paštas doktorantura@ktu.lt.

    Disertacijos santrauka išsiųsta 2017 m. rugsėjo 1 d.

    Su disertacija galima susipažinti interneto svetainėje http://ktu.edu ir Kauno

    technologijos universiteto bibliotekoje (K. Donelaičio g. 20, 44239 Kaunas).

  • 5


    Organic electroluminescent (EL) materials have many advantages when

    compared with their inorganic counterparts and, therefore, they have a wide range

    of potential applications in communications, information display, illumination, and

    so on. Phosphorescent organic light-emitting diodes (PHOLEDs) that contain late

    transition-metal complexes as emitters are particularly attractive due to their

    ability to harvest singlet and triplet excitons, which makes it possible to achieve an

    internal quantum efficiency of 100%. To suppress concentration quenching, a

    phosphorescent emitter is usually dispersed in a suitable host to obtain a high

    photoluminescent (PL) quantum yield. Developing a host with a suitable triplet

    energy level (ET), charge-transporting ability, and thermal and film stability is thus

    the key to improving the performance of PHOLEDs.

    A good host used in PHOLEDs should have the following characteristics:

     an ET value higher than that of the phosphorescent guest, which facilitates efficient energy transfer from the host to the guest and prevents reverse energy

    transfer from the guest back to the host; different phosphorescent emitters require

    the hosts with their corresponding ET values;

     appropriate values of highest occupied molecular orbital (HOMO) energy and lowest unoccupied molecular orbital (LUMO) energy to facilitate charge

    injection from the adjacent hole-transporting and electron-transporting layer (HTL

    and ETL), which is also the key to balance the transporting of holes and electrons;

     high glass-transition temperatures (Tg) and thermal-decomposition temperatures (Td) confer better device endurance;

     appropriate film-forming and morphological stability. In this regard, there is a contradictory issue as to how to simultaneously

    optimize the photophysical and electric performance of PHOLEDs. Generally, a

    highly crystalline film is helpful to transport carriers, but it may also lead to PL

    quenching. To meet these requirements and optimize the parameters which

    determine the device performance, intramolecular charge-transfer, charge

    mobility, and energy level must all be fully considered when new hosts are


    In this field, one representative example is the well-known poly(N-

    vinylcarbazole) (PVK) (Eg = 3.5 eV) for which the polymer bandgap is similar to

    that of the carbazole moiety. Carbazole is among the most stable wide bandgap

    molecules which has been extensively studied for the design of low molecular

    weight or oligomeric hosts, fully justifying the development of polymeric host

    with this molecule. The appealing features of PVK include a high glass transition

  • 6

    temperature (Tg = 200oC), a high triplet energy level (ET = 2.5 eV), good

    solubility in common organic solvents and excellent film-forming properties,

    rendering this polymer of great interest for PHOLEDs. However, PVK is

    characterized by a hole-dominated transportation, limiting its scope of usability.

    Another drawback is that PVK is also prone to exciplex formation, lowering

    device performances.

    Chromophores containing carbazolyl moieties were synthesized using

    rigid and flat structures of aromatic linkage for connecting the rings of carbazole

    in low-molecular-weight hosts. Compounds are prepared by changing the

    connection positions of substitution and are widely used as effective hosts for

    phosphorescent organic light emitting diodes. A shortage of such hosts is a big

    tendency to crystallize, thus the devices can not be formed by spin coating. Due

    to a high demand and necessary complex characteristics, host materials of a new

    structure which could be formed from solutions are intensively synthesized and

    applied for phosphorescent devices.

    The aim of this work is the synthesis and characterization of new low-

    molecular-weight compounds which have electronically isolated chromophores

    as well as bipolar derivatives as potential host materials, and the application of

    these derivatives in multilayer light-emitting diodes.

    The tasks proposed to achieve the aim:

    1. To synthesize carbazole derivatives which have carbazolyl, phenylindolyl, indan-1,3-dione moieties.

    2. To synthesize carbazole and triphenylamine compounds containing 1- phenylphenanthro[9,10-d]imidazolyl moieties.

    3. To investigate the thermal and optoelectronic characteristics of the synthesized compounds.

    4. To apply the obtained compounds in organic light-emitting diodes and describe their characteristics of the obtained devices.

    The main statements of the doctoral thesis:

    1. Branched derivatives containing electric